I. Definitions
As used herein, the phrase “group III-V” refers to a compound semiconductor including at least one group III element and at least one group V element. By way of example, a group III-V semiconductor may take the form of a III-Nitride semiconductor. “III-Nitride” or “III-N” refers to a compound semiconductor that includes nitrogen and at least one group III element including aluminum (Al), gallium (Ga), indium (In), and boron (B), and including but not limited to any of its alloys, such as aluminum gallium nitride (AlxGa(1−x)N), indium gallium nitride (InyGa(1−y)N), aluminum indium gallium nitride (AlxInyGa(1−x−y)N), gallium arsenide phosphide nitride (GaAsaPbN(1−a−b)), aluminum indium gallium arsenide phosphide nitride (AlxInyGa(1−x−y)AsaPbN(1−a−b)), for example. III-Nitride also refers generally to any polarity including but not limited to Ga-polar, N-polar, semi-polar or non-polar crystal orientations. A III-Nitride material may also include either the Wurtzitic, Zincblende or mixed polytypes, and may include single-crystal, monoctystailine, polycrystalline, or amorphous structures.
Also as used herein, the phrase “group IV” refers to a semiconductor that includes at least one group four element including silicon (Si), germanium (Ge) and carbon (C), and also includes compound semiconductors such as silicon germanium (SiGe) and silicon carbide (SiC), for example. Group IV also refers to semiconductor materials which include more than one layer of group IV elements, or doping of group IV elements to produce strained group IV material, and may also include group IV based composite substrates such as silicon on insulstor (SOI), separation by implantation of oxygen (SIMOX) process substrates, and silicon on sapphire (SOS), for example.
II. Background Art
In high power and high performance circuit applications, III-Nitride transistors, such as gallium nitride (GaN) field-effect transistors (FETs) and high mobility electron transistors (HEMTs), are often desirable for their high efficiency and high-voltage operation. Moreover, it is often desirable to combine such HI-Nitride transistors with other FETs, such as silicon FETs, to create high performance composite switching devices.
In power management applications where normally OFF characteristics of power devices are desirable, a depletion mode (normally ON) III-Nitride transistor can be cascoded with an enhancement mode (normally OFF) low-voltage (LV) group IV semiconductor transistor, for example a silicon FET, to produce an enhancement mode (normally OFF) composite power device. However, conventional packaging techniques for combining HI-Nitride transistors with silicon FETs, for example, often counterweigh the benefits provided by III-Nitride devices. For instance, conventional package designs may place discrete components side-by-side on a common support surface implemented using a ceramic-based substrate such as a direct bonded copper (DBC) substrate, or a ceramic substrate on a lead-frame. Such side-by-side configuration can undesirably increase the parasitic inductance and resistance in the current paths of the composite power device, and would also increase the thermal dissipation requirements of the package. Moreover, the side-by-side placement of devices on a common substrate can undesirably increase package form factor, as well as manufacturing costs.